Inventory Shows Decline in R.I. Greenhouse Gas Emissions
January 9, 2023
PROVIDENCE — Rhode Island’s climate emissions appear to be on the decline.
That’s according to the latest Greenhouse Gas (GHG) Emissions Inventory released by state officials last month. The data, which is released on a three-year time-lag, showed the state emitting 10.04 million metric tons of C02 equivalent emissions in 2019, nearly 20% below the 1990 baseline of 12.48.
It’s good news for Rhode Islanders, humanity, and state officials, as 2018’s inventory showed emissions on the rise as the state approaches the first key benchmark of the Act on Climate law. Total emissions for that year’s inventory were 12.70 million metric tons, putting the state nearly 2% above the 1990 baseline, with emissions from electricity consumption and industrial heating and processes trending upward.
If emissions remain stable next year, state officials can breathe easy. The Act on Climate, which opens the state to legal challenges if climate reduction goals are not met, has a first benchmark goal of reducing 2020 emissions by 10% from the 1990 baseline.
The lion’s share of emissions were once again produced by the transportation sector, to the tune of 39.7%, followed closely by resident and commercial heating, which combined to account for 38.2% of all emissions.
Seven percent of gross GHG emissions were offset by the state’s forests (but not wetlands), according to the inventory. For the first time last year, the Rhode Island Department of Environmental Management included carbon capture estimates from the land use, land-use change, and forestry (LULUCF) sectors.
Joe Poccia, an air quality specialist in DEM’s Office of Air Resources, said the agency hadn’t been tracking carbon sequestration due to a lack of data and a lack of confidence in estimates provided by the Environmental Protection Agency.
“We weren’t really confident that the default data the EPA was providing to states was accurate for a very small state like us,” Poccia said. “They were basically taking national data and shrinking it down to state levels.”
LULUCF estimates were derived from tree and forestry data found in the 2020 Forest Action Plan. Different trees species store carbon at different rates; for example, a silver maple tree more than 55 years old can store more than 25,000 pounds of carbon dioxide.
Rhode Island’s forests are 61% oak hickory forest, comprised of red, black, scarlet, and white oak trees. The most common single species of tree is red maple, comprising 27% of individual trees in the state.
“It’s really hard to increase the amount of sequestration that we’re having,” Poccia said. “I mean we’d be talking about adding more forest, which isn’t really possible because A) we have a lot of forestlands already forest, and B) we have a lot of development going on, we’re actually losing forest every year.”
But despite accounting for carbon sequestration, emissions could still be higher than originally reported. Critics say the state is undercounting natural gas — which is made up of 90% methane — leaks from distribution pipelines, compressor stations, production facilities, and other sources.
Studies have found natural gas leaks are higher than traditionally estimated in emissions data. A 2016 study published in the peer-reviewed journal Environmental Pollution, showed that just 7% of methane leaks in Boston accounted for up to 50% of all emissions.
“[DEM] is using a 1% leakage rate, which is totally unreasonable,” said Timmons Roberts, a professor of environmental studies at Brown University. “It’s unrealistic. It’s at least 3%.”
Roberts said the state needs to use the latest Intergovernmental Panel on Climate Change (IPCC) factors when calculating emissions. When reporting climate-altering emissions, the state bases its math on guidance from a 2007 IPCC assessment. Using the latest assessment, released in 2021, would make the global warming potential — the impact GHG has on the climate — almost 20% worse.
With a whole basket of GHG emissions, how do you measure all of them? Methane and hydrofluorocarbons (HFCs) stay in the atmosphere from less than a year up to a few decades. In comparison, C02 sticks around in the atmosphere for centuries.
There are two methods to account for GHG: by 20-year global warming potential (GWP) and 100-year global warming potential, each weighted toward how long a certain tranche of gases sticks around in the atmosphere. Global warming potentials are multipliers that attempt to equate the impact of shorter-term GHG emissions with carbon dioxide.
Roberts said the state should use the 20-year GWP. “The impacts of climate change are coming much faster than people thought,” he said. “There’s really no sense in averaging this all out over 100 years when the damage will be done in the next 20.”
Combining the undercounting of methane leaks and weighting for 20 years of global warming potential, means statewide emissions could be as much as 45% higher, according to Roberts.
Rhode Island remains one of the lowest GHG-emitting states in the region, just behind Vermont in terms of lowest total emissions. Environmental officials expect the 2020 inventory to be an unequal comparison to 2019 thanks to drastic lifestyle impacts from the first year of the COVID-19 pandemic.
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